The use of chlorinated, aromatic hydrocarbons as modifiers and plasticizers for plastic and rubber compounds is well known. Polychlorinated biphenyls, for example, have commonly served in the past as a major source of plasticizers for polysulfide rubber sealant compositions, due to their unique compatibility with such compositions. Recently, however, it has been determined that certain of the most widely-used polychlorinated biphenyls are accumulating over long periods of time in the environment at undesirable levels. This continued presence in the environment of the polychlorinated biphenyls is due to the fact that they are relatively stable and tend not to degrade. Often, rivers and streams are polluted by the dumping of polychlorinated biphenyls as chemical plant waste material. Once in the waterways, the polychlorinated biphenyls are a toxic pollutant which is very expensive to remove and highly destructive to the environment. Even when incorporated in synthetic resin compositions, for example, in a polysulfide rubber sealant formulation, the polychlorinated biphenyls are a source of environmental contamination, by way of sealant decomposition or minor plasticizer exudation.
As a result of the severe environmental hazards posed by the continued use of polychlorinated biphenyls, their manufacture and subsequent incorporation into polysulfide rubber sealant formulations has been virtually eliminated.
In recent years, increasing efforts have been directed at attempts to provide a substitute for polychlorinated biphenyls as plasticizers in plastic and rubber compositions which has the necessary compatibility so as not to exude or bleed off in any significant amount from a cured polysulfide rubber sealant composition into which it is incorporated. Such exudation causes an undesirable loss of adhesion in the rubber product. Chlorinated liquid paraffins, which are less stable than the polychlorinated biphenyls and more readily degradable, thus eliminating any possibility of environmental contamination due to long term accumulation of the contaminant, have been investigated. U.S. Pat. Nos. 3,770,678 and 3,925,331, for example, generally disclose the incorporation of a chlorinated liquid paraffin into a polysulfide rubber sealant or caulking composition, and are herein incorporated by reference.
U.S. Pat. No. 3,770,678 discloses a polysulfide latex-based composition consisting essentially of a water dispersion of a particular high-molecular weight polysulfide polymer, a particular polythiol polymer, and a special purpose additive selected from several compositions including plasticizers. Among the plasticizers mentioned therein are chlorinated biphenyls and chlorinated paraffins.
U.S. Pat. No. 3,925,331 discloses a curable sealant composition which is the reaction product of a polysulfide and a mercapto group-containing silane which may include a plasticizer and/or a filler. The plasticizer may be selected from, amongst others, chlorinated polyphenyls, nitrated aromatic compounds, phthalates and chlorinated liquid paraffins.
This prior art suffers from several serious deficiencies. First, it fails to recognize the environmental hazards of incorporating chlorinated polyphenyls as sealant composition plasticizers, as discussed in detail above. Further, many of the plasticizers contemplated by these broad teachings are too volatile to be successfully incorporated in or are incompatible with a stable polysulfide rubber sealant formulation. Further, many of those plasticizers can not be readily incorporated into polysulfide sealant formulations in amounts large enough to result in an economically priced sealant.
Japanese disclosed patent No. SHO-48-59151 teaches the incorporation of chlorinated paraffins as plasticizers for a liquid polysulfide composite. This prior art, like the two United States patents discussed above, fails to appreciate that such plasticizers can be too volatile to be formulated into an acceptable stable polysulfide rubber sealant composition, and/or can suffer significant heat loss, and/or can be so viscous as to be virtually unworkable and require dilution or cutting with other less viscous materials.
The incorporation of a chlorinated alpha-olefin containing an average of 6 to 18 carbon atoms per molecule and generally from about 20 to 73 weight percent chlorine or a chlorinated paraffin containing an average of 8 to 16 carbon atoms per molecule and generally from about 10 to 75 weight percent chlorine as a plasticizer generally for plastic and rubber compounds is also known. Particular examples include, e.g., products chlorinated to from 50 to 70 weight percent. See, for example, commonly assigned U.S. Pat. Nos. 3,896,183 and 3,919,338 which are herein incorporated by reference.
Again, there is no recognition in these patents or any of the prior art of chlorinated paraffins or alpha-olefins which are rendered compatible and non-fogging in a polysulfide rubber sealant formulation, which paraffins or alpha-olefins may be incorporated with a liquid polysulfide polymer to form a stable polysulfide rubber sealant formulation.
In summary, attempts to use all of these known chlorinated paraffins and alpha-olefins as plasticizers for a polysulfide rubber formulation have proved unsuccessful since these known plasticizers do not exhibit the necessary high degree of compatibility with a cured polysulfide rubber formulation while still retaining satisfactory volatility and viscosity characteristics, and the search for a satisfactory plasticizer has continued.
It is, therefore, an object of the invention to provide an improved chlorinated hydrocarbon composition which is highly compatible with a polysulfide rubber sealant formulation while still retaining a satisfactory volatility and viscosity for use therein, and which is non-fogging.
It is an object of the invention to provide an improved chlorinated hydrocarbon composition which will avoid the problem of environmental contamination due to long term accumulation.
It is an object of the invention to provide an improved chlorinated hydrocarbon plasticizer which when incorporated in a polysulfide rubber formulation will avoid the problem of environmental contamination due to long term accumulation.
It is a further object of the present invention to provide an improved polysulfide rubber formulation which incorporates a highly compatible chlorinated hydrocarbon plasticizer having a sufficiently low volatility and viscosity, the polysulfide rubber formulation not being subject to significant weight loss and the chlorinated hydrocarbon plasticizer not being subject to significant heat loss.
It is a further object of this invention to provide an improved polysulfide rubber formulation incorporating a chlorinated hydrocarbon plasticizer which eliminates the possibility of environmental contamination due to long term accumulation of the plasticizer in the environment, and which is useful as a glass or window sealant.
Other objects include the provision of methods for chlorinating the improved chlorinated hydrocarbon composition and for preparing the improved polysulfide rubber sealant formulation.
These and other objects and advantages of the improved chlorinated hydrocarbon composition and polysulfide rubber formulation incorporating the same, as well as their scope, nature and utilization will be apparent to those skilled in the art from the following description and appended claims.